Dear Peter
I am extremely sorry to tell you that I am unable to go to your party this Sunday. It is very kind of you to invite me to your house and I hopefully want to celebrate your birthday with you and express my best wishes to you. Much to my regret, I will be absent from your party owing to the fact that the College Entrance Exam is just around the corner, for which I am now quite busy preparing. What’s worse, I have caught a bad cold lately and I am really not myself.
I am truly sorry. I hope you will forgive me and accept my sincere apologies. I believe we will have many more chances to get together. Shall we make it after the Exam?
I’m looking forward to your reply.
Best regards,
Li Hua